I have a JR 921 RX on my Trex 600N, and I had an AR7000 on the Xtreme 50 which is now designated for the 700N.

Should I simply install the 7000 on the 700N and be done with it?

Put another way, the 9CH RX is a 2048 RX, and the 7000 is a slower 1024 RX. If you had both RXs sitting on the bench, would you install the faster 9CH RX in the bigger 700N, or in the smaller, more nimble 600N???